DA0-002 Data Acquisition and Preparation Practice Question
A data analyst is tasked with combining customer data from a CRM system and a billing system. The CRM uses a GUID for customer ID, while billing uses an integer. Which approach should the analyst use to ensure a reliable merge?
⚠ Common exam trap
Watch out — candidates often assume customer name or address are sufficient join keys due to their human readability, underestimating the importance of unique, system-agnostic identifiers for reliable data merging.
Answer choices
Why each option matters
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Standardize the customer ID format and use it as the join key.
Standardizing the customer ID format (e.g., converting the billing integer to a GUID or mapping both to a common string key) ensures a consistent join key across heterogeneous systems. This eliminates type mismatch errors and guarantees that each customer record can be matched reliably, as GUIDs are globally unique and integers are typically sequential, so direct comparison would fail without transformation.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✓
Standardize the customer ID format and use it as the join key.
Why this is correct
Standardizing keys ensures a consistent, unique identifier for accurate merging.
- ✗
Use the customer name as the join key.
Why it's wrong here
Customer names may have variations and duplicates, leading to incorrect matches.
- ✗
Merge using a cross-join and then filter manually.
Why it's wrong here
Cross-join produces every combination, which is inefficient and impractical for large datasets.
- ✗
Perform a fuzzy match on the customer address.
Why it's wrong here
Fuzzy matching is unreliable for exact record linkage and may cause false positives.
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Written by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
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